Signaling-circuit.



Patented Jam 2% 19% s sHmiTs-SHEEI 2.

A TTQRNE' PHGNE ANDTELEGRMH-Gommyrig Q cmmmmmmw @E NEW @wam To all 'wlwm z'tmxy concern l l Beii; known that L Gaona@ A. CMPBELL,

. residing at Montclaindn' the @Gumy nf ES iii' natng 'at the. same station. ,La other words line. Itsubjeti; -topnod@ i@ signaling cir-- cuit arrangement W'hrlh in coperatm comm bination with z'smilar andequal commun-1u cfitig'mr'agement or simian' .fdc-.ail (ever the'mgximumfamount of enegy to the 11estation, orl'grranggement. A fu'rzher f wbjecwt is to plovlde im vmmangemmat smh that th@- ferenca y Vtha transmisson `allergy Grig its obgect is to prmtidesgnaing mamasgharacterfzed by the. maximum possible mtl@ nf I recei'vfgd to tzfgnsmitmd: energy mui further ais *Gymline cfgivehrimpdance und iengthf.' ambun of ehergy gbsprhdbythe receiver I. muv n nrdnata reqmrernents winch are maessary in" its more specific Shah be negligibe sid@ tone in' the rfecaiver the -neg at si small samjifce of efficiency against dimm-hing; line noia@ nie; dstim giished from thetelphoni'csignals jfmm mm3.. t is furher ideal in than sense ihm; a.

minimum number of femm is empwyef lsince at lamb ane; auxiliary 4emtment. is weesp sm? to secure :redom-from side tone.

im auxiliary resistance, elemenf, necessary as it. is tog Secura :fr-eefum from side ione, Wmsl'y at the' same mme necess'a rik?v reduc@ the 'eff cigncynf 'tbs substation sing@ energy is'nmn avmdabl? Wasi-ed ms'aif auxiliary ressb @mce. Tat tins 1s not the case and tmi; .tlm

eicefncy of @h substation ofmy invention s s@ .hem'etica maximumywhich cannot be side/mithin@ wl how. The :simplest fom of trns'njltter are nonnected in series with ach l @than across the lhrw. In auch sm' arrange ment the @ver-ull efficiency is a: maximum when he resiatamz of tha receiver is equa mity to thath of the transmitter. When this condi tion is satisfied obviously fifty per cent. of the ener-gy delivered by the l'ine to thesubstation is Wasted in the transmitter and fifty per cent. of the energy delivered by the, transmitter is Wasted vin the receiver. Further such anfarrangement labors under the disadvantage of full side tone. In the substation of myv invention fifty per cent. of the energy""delivered by the line'to the substation is WastedV in the transmitter butV none in the auxiliary resistance if said auxiliary resistance and saiclline-arev conjugate; hence the eliiciency is as great as that of. the simple series substation. y When transmitting` no energy is Wasted in the receiver but fifty'per /cent. of. the energy delivered by the transmitter is Wasted in the auxiliar resistance. The vtransmitting eiiiciency is therefore also a theoretical maximum and neither transmitting nor receiving eliiciency is reduced by the addition of the auxiliary resista-nce Which-:isnecessaryrtom'sceiire'free# aol dom `from side tone. The foregoing consideration .will serve to explain thedesirability of'having the line and auxiliarv resistance conjugate as Well as the transmitter and,i receiver. V

In my present invention I `provlde a snbr station comprisin'g/ transmitter, receiver, auxiliary `resistanceand transformer and so proportion said component elements and so relatethein to a telephone lineI and to'leach other Ythat,in combination with sa'id'telephone line, said substation satisfies all'of the foregoing requirements.

`.I vhave discovered that thc above-men tionedrequirements may loev satisfied by a ylarge, iniuigberV of' arrangements er'r1plo 'y1'n, `r

the minimum .number of elements and allY ernia-Hy efficient Vand Without side tone. l/Vhlle theoretically allV these arrangements are equally rfgood, practical considerations v lua-lm oertain arrangements preferable.

drawing in which:

Vgrams lit-,nig so arranged My invention. will .now he fully understood' hy reference to the accouinanving y 1.6117 and 21 are sche- 4matiqliagr-ams oi sixV 'Forms oi suhstati'ons in .accor-(larice u'ilhv this invention, said diaasto clearly indicate the eqiiivalcnf'e ol the dili'crcnt circuits;` Figs. 2, f3, l0, 14, 1H land 2'2 are rircuit` diagrams showing* the arraufgouwnt of thel iseveral lornis ol"sul' sl:'|lou`s in gri-atoldctail. I5, 7. ll, l5. I9. aurli are vii'- ylugares 1. 5', i),

v cuit diagrams indiening the relative din-etion-'ot curi-ent llow in"`l hc Several circuits shown nieblas. E2, t5.. ill, i4. I8a1ul'22, re

s|wftitely, lilil'iufgl ll-'rilfisniissioln the dotted l sonrlu-:alum` n h-nuuls through which no was, 4; s, 1;, 1o. 2o and` 2i Trams indicating hc relai-ive current flows .ne sinillar di' i directionotxcuireut' llow duringr reception.

`lu theahovwdiag'rauns the direction of wind-V ing ofthel transformer coils andthe direction of current fiow as indicated are symbolical and only hold true for particular values of the elements of the' substation.

It will be clear from an inspection of the design formulae hereinafter set forth that the Winding ratios r and r may, in general, be either positive or negative, depending upon the values of the line and transmitter resistances. If, therefore, for an particular design'one or both of the win ing ratios results in: a,nega'tive value, it is to be interpreted as meaning that the relativer direction of winding of the coils Whose Windingr ratio is negative must be the reverse of that shown in the diagram. y' Y 'In order to' illustrate the scope of my invention' and Ielucidate the principles on which all specific embodiments rest, a general theoretical discussion will now be given which applies to all suhstatio'ns satisfying the requirements heretofore V:'-atated' in this specification." In 'this discussion and the equations and formulae included in this specification the subscripts 1, 2, 3 and 4 will Vreferto transmitter, rcccivcr, auxiliary resistance and line respectively. Thus "l1, I2, I5, I4 will denote the currents {1on1-ing in transmitter, receiver, auxiliary resistance and Iinerespectivihly, While R, will denote the resistance of the transmitter, R2 theresistance of the receiver, etc, f

Consider a substation consisting of transmitten, receiver, auxiliary resistance and approprlate transformer windings, connected to a line of given impedance. In practice the line connects two similar and equal suh stations between Vwhich `vconununication is established. It is'a well known principle thatiif a terminal Vimpedance is connected to a source of electromotive force through a lineofiinpcdance z=n4+m' where It, is the resistance and It', thereactane component ot' the impedance, the terminal.' impedance Amust be ltl--ilt4 for maxi*- mum absorption ot energy; lu'luirtlcular r.ii the line impedance hasno rcactancefeomponent, thc impedance ot the'terniiual arrangement as sveufrom the lline should be equal. to the resistance con'ipouent of the impedance oit/thc line. that the substation lshall havemaximum elicrgry labsorption i'rointlie line is that its imomlance, as seen Yl'rom the line, shall be f|iial to the line iuipwlance.' Y v 'The 'significative' of 'the .'loregoing stateinuutmay he explained hy reference to Fig. 2, as lol'lows: 'Letlhe substation he disconnected from lho lini-l and let the impedance ol.E the substation he uu'asureil across tcl'riiifi nuls fr, and Thi-n the impialance A,sonicasured shall he equal lothe'unpetlauceu'f the line, 'Witli'tlm huemmnated at ear( d The comlition,then,

by a .substation 4szitsnfying thie eondition,

the line maybe replaced, es regeifle trans mission from either substation, by an rimpedance element of resistance eqnei 'tothe 5 impedance of the line. `Any reaetence effect, which isin practice smolLfmey be climi noted by neutralizing reaotanoe moet there fore, need not be considered, The condition, then, Athat the subetation have maximum 1G energy absorption 'from the'li'ne iethatjits impedance as seen from the line be 'a pure resistance-of value equal vto the impedance of' the line, This Condition. is evidently equi'vfi lent to the' following requirement; let an electromotive force be impressed on the sub ,stotion-terminals through a i'eeietenoe equal lto theimpedance oi the line; then the energy consumed in the substation shali be equal to the energy consumed. in seid resist 2() ance.

` Further, line andeuxiliary resistanoe are conjugate by requirement (2)5 as hereinbefore S'tatecl, o1' in oti'lee wo ls the auxiliary resistance is connected to' points of eqiiai v potential with respect to eleetonnotive forcevapplietl to the line terminale. Moreoveigthe impedanoe 'of the snlostetions ae Seen from the Eine should be. equai to that ofthe line. Let, then, im' electiomotive force E4 be im'llvressed 'through e resistance R,1 one substation Whose' transmitter and receiver' resist'zinces are 'R1 and R2 1'espe-- Since the energy eonsumed'oy the subsite tion iseqmil to that ,consumed lay the re-- sistance R4 and therefore one-heli of the totoi eneigy consumed, itfollows th at,1"equirement 4 mavbe 'formulated by theffollowing:

in the .sin L, etion, aml-that'the substation lis equivalentia'e seen rjomjfthe iiiie, tota :Ce-f sistance of-Vnlne v A n'irnilonely,4 if transmitters ami .receiver conjugate the condition that the tmnsmittef 35 shall have its maximum outpiit to line and To complete the auxiliary resistance may be f nnfmlgitedlv es" :tollonvsr'v Let im electromo'tiie. force E1L in the transmitter produce 4currents IU- L end Ia intranemitter, line and' auxiliary resistance. Then', for mximum outpntit folf, .70 lowe'that (INR, 'm (INR. WRF (El Equation (2F15 the anale ne oteqiiation 75 (l end may e'inteiprete' as follows by re 'eretico to Fig-.2, llffetthelt ifeinsmitteribe disconnected from, the ternfiirwils;` b and ,off

and let the 'impeden'oetbe measured zeroes saliti-terminate. Then 'if `equatiovn (2) is 'Se sattiedthe impedance so meaeuredjis'eqiial to the linriped,:in oe of the. transmitter. In

other wordsy the impedance of the combinate.'

tion as .seen from thetransniitter ie eque! embodiments'of myinvention, equetionif) oliows as i conseqixenoe of thefoonditions of double* conjngacy and eqiiation (1);-

Therefore the foregoingfour requiremen ,impose but three. eetiietioiis onthe subst'f;

tion.

meins to consider the energy division Vbetween receiver and'tlansmitter `when reeeixzf 4B I ing, and between'fline"and-auxiliary 'resist-- ancewhen transmitting. Let W0 be the totajl amount of telephonie energy' developed by.' the transmitter et the transmitting subetaj tion; themfloyv equation (2)5 1/2'VV is the amount of energy delivered to line and aux.-

lll() iliacy: resistunoe: Let `the' amount-.of energy .teken by the-euxihary resistance be mtimee" that taken by the line, then the amount' of" enemy teken by the line is in@ :so that the' transmitting eflioienfoy is "mees- 1 oreal by 1 Wwf? Ouf, the total energy delyereol to-tho re-j" oeiving sulostetioii, let-the transmittenfab. 'M15 Sorb y timesvthatbeonbed. by the Areceiver.;.-5 y

' then' thereeeiving eliicienoy:ie-'measure'dfbyf Y f The-oiferalleiieiency from transmitter-of :'-1 one station to i'eoeiyerof communicating* station is clearly proportional to the prod- .uct of. the trnsmzxssxon"efficiency and receiv? If :n and y were independent, clearlythe general discussionjt re,- V .Y

Gel

vtlm onrron flowing' in Ens-qll.'

and e. The lino L ls communi-nd bewaren terminals a und e. windings N, und NZ nro tlxeflo'w of' dirent currn', so that 'direct ein reni; from n dlstunt central olo full flow vover tho line o 'terminal af, 'through ,Wm-omg; N1: 'razasmll'er T, rec-errar l., trarduring 111mm n a. :al Series circuit: with the, winc' Nic The, mlnatlon ofthe frnnsma/or mu rnl'smlater, its 'zwflon boing oonwulon; no Seging' up m the transnnter u van-labio oleo? trnnlotwo foroowlnch .mr nllern ating vsurfent to How, it a given nsjon of timo,

therefzjro, u.. current L'lows 'from tormmrl 0 hronghlhe tranfnnter o termina-l and thence lne-lr through the winflng N2 'to ler-- xninnl c. .An induced curro-nt. L @qual .to la is thereby musa-,fl to llow from ormlnnl through rhewincl'lng N1 over lille lino L lo tmslnnf e. lul-@Hgh tbemmilnry rossmne ton'm" al :s: :un inmzcod in tho il au] sformfergw nfb of Snclr vaine und d" action to .lower -ll ponllnl of in@ pointv a 'nes-ame po lientm as point; c, so ihn-u no mirront; flows through vthe vrasoir/er during' transmission 1nd the substation. is, thm:ef'oro7 nntifsdo inno.: y i. i

Tho aclon when rer-3 kring s indicatedv Ain llig. 4i, in. which tho zrro'ws indicate the rela lro drocton of curront low und tlxn'dotfocl line@ nolinioy elements lllrongh, which no 1 flows. Sino@ no ourront lows-lirough nary res.st ance, tlw rrooorer und n serien crcut and n potential .infill lo the lin@ cameos n'. current lli. equal E in flow from terminal-0, throng-h inline reoornr R7 over the lino L to lthe terminal a., llrongll the` Wnrlng N1 toi/lm terminal Z1* A current If-flows from *borinlnal c lo orni'ml bfnrnu'gll lle winding; N2. 1; tormnm 32 the two on reni-,f5 Combine and x onrront L {ows from torn: ml b through lao lrunsrnltor o torminn lotnntnls aro imho-exil. in-rho transform@ mnn's who imo. l'lxporlenC-o has shown that, thea@ a., nxding of nnolr vzlluo nml dretion that. the terminal d is reduced 1.o the same potential as terminal e, so thm, no curl-ont flows througl'l #he nuxil. lary rcsslnnoe. Consequently no energy loss occ-urn in. tho auxiliary resistance and while Horno onorggy is lost in ovorcomng the lmpedv anco m tho trnnmiltur, such loss; is no greater d1un tho transmitter loss in a, Stumlnrd substation I The proportonng of the arrangement of lfL 2, or im equvnlent, Figs; 3 and 4, to sans Q 'y rho fundnmenml roquroments of tho annotation of my in vontion, will non? be giron ln deriving 'the design formulae, linx?, rosslancos 'of the trzmsformer'windings Wll loo ignorod and the resistance ot'he winding Nn '1n Fig. 1. will bo treated as si, @aparato clement, ll'ffll be assumed further llniz more is no magnetic leakage betwn 'rho transforme-r*windings and that tlm. golf rn'redunco are very large comparofl with, the rnsfzrlnnces of any o?. tho component eloo laire substation or lha-1 impedance of smpllying assumptions jnsiorl and 910 phat the :Lssmnodconditions may be closely lined in pracuco by czleful iloslgn.

To orn'rnlate the Condition for conjugao'y nl? lrnsmijLP-r T and. receiver, E? nssumoan elocromotve force "in the transmitter 'cirr-l cn'l, and assumo that the roquiril condition olj oonjugaey is .satusfoc` Inotler words,- asf'lnno that the terminals o" thorecever v nro at points of equal 'uotenligl 'with respect. to 'an oleotromoytlvo orco npplolv to :the `41G@ transmitter. 1 Il, l; I, L H12-noto the 'Curr'. rents lo'wing; in the trnnsmiter, tho: recevor, A' :auxiliary resistance and line,- respectively, :mil l'l, ,Rwal' and denote, the' rosi-stunoea :7 of the', enrlfkrspomlng elements. .lleCond-l 105 on of conugocy of the rof..,v'1ver-With re- Spool, to lille trunsmlior requires that. no 1 cnrront vflow through the socorrer and branco REGL 17: is also cloarfrom Fi, 3 that durn 1 I' a n l l h n lng transmxsslon 13:: y Slnce the potential 110 drop across 'elle recolvr rnliStloo zero, terml'i nuls c und. @are at the same p otntal anl'the nlgolorncsum of the potential drops through o the windings Ng'znl Nw'nnd the IR drop through-be auxllinzry rosstanoo X,'Inusf be l Dosignating thodrop; portnrn K oppose each' other as regards a 'circuit'lv in' which they are serially includod., the Condiequal tothe'drop through the windings N1 Substituting the values given by equation 8.

and N3. -This condition may be expressed in equation 2, we have as follows:

i R414+RsIs=Kn1+Kns or I (R'l-R4)Is=1(n1l"na) Combining this equation with the 'last preceding equation, we have i R+R.=m+m R, 'na-n, whence R4 :nl il'nz Also the algebraic sum of the ampere turns I of the transformer windings must be zero Y have so that I1nz=I4 (nfl-na) Since 13:14, this rcduces'to Referring now tol Fig. 4 which shows the.

Kad-RzIZ-:Kas

Furthermore since the transmitter is 'in a series circuit with the Winding N2, the algebraic suln of the dr f through the winding N2 and the IR drop tlirough the transmitter must-be zero, so that R,I1=Kn2. idii'ibining these equations we have Ra/zgnafnz t 'I n. Furthermore the algebraic Sum of the ampere turns ofvthe transformer windings 4 must be zero so that n1L=n2(I1"-I4)' or l 4 71211:: (n1-P71014 Y from which it follows that their.. 4- n:

'Combining 'this equation with preceding equations and remembering that I=I` Vwe Rz ('ns" (n: 'l' nd)- R: (9)

I. i i n I: 'nx'lna (-10) Substituting the values given byequation 10 in equation 6, We have,

Collecting formulae we have the following:

aging-na (man If, in the above formulae, we write the ratio-1 as r, and the ratio las 1", we have 3 the following; a

Substituting this-value in equation (b) 'of the above group7 We get l Eazy/R4 (15) From equation 14 it followsvthatw From equations 16 and 17, we get ..f1:; L: RV T *i mim/" Byicombining equation 1i with the preoed ingiequ'altiomit is 'apparent that iiowfwe designetethe right-hand term -:of'equation 18 ns1?- and collect, we have es the-ifdesigne.foimmilee4 olthe subetation oi' Figs. 2, 8 or 4 tliefollow'ingcf i the? retiols'w endif 01? thetrens 40 forme the" resistencias off the" line and transmitter- *findiythe eonstent y. Having, oh'osen these tlireenvaluesftlie' remairiirip; elements of theV substation' may be readily determined.

clieolA form-oi"- substzition issllustrate i1 Eifg .a6f=in 'Wliioli the' oo nneed: nf series-With the.

'a rellelf therewith .between high-resistance wind'-i receivers is connected 'between ter- The operation timing transmission will be clear from Fig. 7. Since no: ourrent Howe N5 so that e variable potential IWinding N3 to terminal L other only in the conuetion, 'former Wiriclmge.

thefresisteriee'ofthe liuezand the constant .ndirig'l-Tl be tweeiiite @mele wende emi the Winding NLE :is obuyiieotedbetween -teruiiinee' a' and 'hil'e the' line is* connected he high resisten-ee Winding ngfo-'negligi- 'i e' separate resistance' ele` through the receiver R, the transmitter is in n local series circuit with wiudmgs N, and

afiplie'd et the transmitter causes e current l to flow from terminelc through illetrsmemittr :iud' through windings; NX and N2 to terminal e.

An induced current L equal to I3 flows from terminal (i over the'line to terminal e and then through the eulrliary resistirme X and. Potentiale` fire induced iri the transformer windings of'such value and direction' ilrizitl points c and e are brought to the seme potentiel so that lrio eurrene flows fliroitlgl'i the vreceiver during tranemissio'u.

During reception, es indicated in Fig. 8, since no zurrent flows'througii the auxiliary resistentie, the receiver and line are in a se ries circuit and e potentielfapplied to the 'line Causes a current L @quel to 12 to flow from terminal 0 through the' receiver R uml over the line L totermiuel a. A current L Hows "from terminal -c through the trauemitter T and winding N.i te terminal of., While e current lfl flows fromtermnel i through, the Winding N2 te terminal o. we

' tentiels are .inducedv irg tlie transformer windings of suoli velue lemi direction that terminals d emi e o the auxiliary reslstzmce are et the seme potentiel. so that-"no curreet flows through seid resisteueei,

A comperisonof the ciegrzrms olige. l, 5x, 9, 13, 17. endvlslioiis that the several Substetione lie-rein-i51:.leelE clier from each the'trens- 'Referiirlg o riesige formulee A for the substation Fig. 1, it will be seen 'that the expressioie 'for the receiver resistance and auxiliary reeistgiuce, es given in the iirst two formulae ofthe group', are

'independent ofthe iet-ies of 'the treneformer windings that. these expressions will hold true v'for allf the eubstzitiois herein dis- 'closed'. THe remaining design formulae for the substation of Figi@ 'may be determinel from design formulae A es follows;

Rewriting formula A We 'have (Affi l "lig-lili W Rryu 'F') I Referring to Fig: 2, the number of turns of the trensermer'rvindin-gs connecting ter New,

f se

lin Fig. l0. In

minalsa'and o, a and o and a and d, may be expressed as follows:

Nub=n1 Nim mol-rn, Nad :ni Fna windings may then be expressed thus:

Substituting these values in formul' Aand designating -the expression 'Rit/(1 +r) as P, we have as the general design formulae for all of the lsubstations herein disclosed' the following:

From inspection of Fig. 6 it will bel seen that .Nnbzfl'l acF-Tnz fm1-77's Substituting these values in the last two equations of iormulze B, we have as the corn 1b i If be written as r, and be Wlltten as 3 r', we shave as the design formulae for the substation of Fig. 6, the following:

naiven?v The ratios r and r of the transformer' through the transmitter said terminal, from which point the current responding formulae for the substation of tials are induced in ment the transmitter T is connected between the terminalsb and c. The windings N1 land N2 are connected in series between ter minals a and and at their junction points are connected to terminal c through a conf denser. The Winding N3, which is of high resistance, is connected between terminals b. and e, andthe receiver R is connected between terminals c and e, while the line L is connected with tern'iinalsa and e. Instead of a high resistance winding N3 a separate resistance element X may be used as shown in Fig. 11,'with avwinding N:K of negligible resistance connected in series therewith.

VDirect current from the line flows from terminal a through windings'N2 and N, in se ries, to terminal I) where the current divides, part flowing through the high resistance winding N3 to terminal e, and part flowing T and receiver R to returns again over the line L,

The operation during transmission is in'- dieated in llig,y 1l. The actuation of the transmitter cau/ses a currentIl to How from the junction pointot windings N1 and N2 through the Icondenser to vterminal o and through the Y'transmitter T to terminal Z). At terminal the current divides and a c urrent I4 vequal to I3 flows through the windlng N3, auxiliary resistance X and over the iineL, to. the terminal (1, and thence through the winding N2 to the junction point of windings N2 and N1. A current L--JLi i'iows in 4parallel therewith from the termina] b, through the rwinding N1 to the junction point of windings N1 vand N2. Potentials of such value and direction are induced in the transformer windings as will reduce the terminal e to the same potential as terminal e, so that no cur en t flows through the receiver. l

During reception, indicated in Fig. 12, a current Lequal to Iu'fiows from the line through the winding N and the condenser to terminal c and thence through the reand back to the line L. An inv duced current I, flows from the terminal c, ithroughftl'ie transmitter, winding Nl and eeiver It back to terminal c. Potenthe windings of the transformer-of such value and direction as to bring terminals d and e to the same potential, so that no current flows through the auxiliary resistance.

The design formulae for .this substation may be determined from the general design formulae B, as follows: Comparing Fig. 10 with Fig. 2 it will be seen that the number of-windings connecting terminals a and a and c and a. and d, respectivelv, may be expressed as follows: Y m 'V the condenser,

Solring the above equations for n and n2,

Y vformulae B and wrlting the ratio as. r,

' 3 ndi??a as 1r', We have as the deslgn formulae f l'r substation of Fig. lthe following:

L 1n.: the modification illustra/ted in Fig. 14, the' transmitter Tis v'connected in series with iithefwindingrN, between terminals a and c, iiurliile the winding N2 is connected in par- -n-uefallel;ftllerewith. 4'lhe 'Winding N2 of high esistanee is-jeonnectefl between terminalsv Z1 rnd d.v The 'receiveuR is connected between -er'minals o ande and the line L is connected between terminals n. an'cl'e'. A condenser iylie inserted in series with the winding N2'to determine the path of thc (lirect cur- :rent tlowingfthrough the substation. The direct current from the line flows through -the Winding N, to terminal l), at Whioh point the current divides, part llowing through the Winding N3 'to terminal e and part flowing through the transmitter T and receiver R to terminal e, from Which point the current flows yback over the line. The high resistance Winding N3 maybe separated uto-a low resistance-Winding and a separato resistance ele-nient X :is/Shown in 155 and 16.

il l 3.

the winding N2 and the condenser in series therewith to! terminal unnl thence through,

the transmitter -T to terminal b, A current 1,1-2 {'lQu's-froln terminal rz., through the Win(li'n g .N' to teirniinal.:iir` `At terminal 7 the twoo'urrents unite'anila current: 1 equal -rs'ta'ncev` X to terminale, troni vWinding N1, to terminal a.

l' l' he operation during transmission, as in-4 current I, to tlow' from terminal (L, through 1 nt -thelcurre'nt flows back o'ver the' ries circuit, so that a current I2 equal to l2 flows from terminal c, -through'the receiver It and over the line L, to terminal a. A current l'1 f iows in parallel therewith from terminal c, through the transmitter T and At this point theeurrents unite and a current I2+I1 lows from terminal a, through the Winding NZ tively, may be Written as follows:

From the aboro equations it follows that N#-N 'n2-n, I

NM"NE: n3 Substitutingthese values in general design and formulae B and Writing as before gli as r, 2

n I I .l and qb as r', we havev as the design formulae for the. substation ofFig. .14 the folloiiving:

AIn the modification illustrate@` in Fig. 18, the transmitter T is connected in series with winding N, between. terminals a, and o, the Winding N2 is connected between terminals o and :Z andthe WindingI N2 hetween termi and the condenser, to terminal 0. The ponals a and (i. The auxiliary "esistance XA is I connected between terminals ci, and c2-the re -eeiver B betiveen terminals e and e land the `line L between terminals a and e. Conden-v sers are inserted in series'with the Winding 'N2 and thenuxiliary resistance X, as indi# cated, to (letorn'iine the path-of direct curf troni :i list-ant source Willflow over'the line L, through "the winding N1, 'transmitterT," receiver R, tu terminal e, and thence" back 12 winding N to 'tern'iiual rz.' A current I3.v equal to I2 'Hows in parallel therewith lfrom 120. rent through thosubstation. Direct/current. '1

v terminal d, through resistance X and over the line L, to terminal a.

' i a current Id-I.L

Durmg reception, a current I4 equal to I2 flows from terminal c, through the receiver R and over the line L, lto terminal ai, lwhile .a current l1 flows in arallel therewith through the transmitter and winding N l to terminal a. nal d the currents vrcombine and a current Irl-I, Hows through' the windings N3 and N2 in series to terminal c. Potentials are induced in the windings of the transformer Substituting these values in general design formulae B and wrltmg the ratlos and 3 Tf as r and 1"respectively, We have as the .dlesinv formulae for the substation of Fig. 18 t e following:

Still another form of substation is illus trated in .l.i`i`g. 22 in which the transmitter T and .the winding Nz are connected in parallel between terminals and (awhile the winding N1 is connectcdbetwecn terminals resistance Winding N., isl terminals a connected between terminals c and e and the line Lis connected between t'enninals aand e ing N ,l instead N3, 'a l ofhigh resistance winding 0W resista-nce Windlng and a separate to terminal as indicated in Fig. 20,

tial,

seen that isigu formulae B and former ratios'as r and in yparallel with the windresistance element X may be used as indicated in Figs. 23 and '24. A condenser may be inserted in series with the winding N2, so that direct current from 'rom terminal a, through the windingNa, e, and in parallel therewith, through the WindingN 1, transmitter T and receiver R to terminal c, :tromA which point the current flows back over the line.

During transmission, asV indicated in Fig. 23, t e actuation oi 2 the winding N2. An induced current' l, equal from terminal a, over the line, to terminal and thence through the resistance X and tentlals are induced 1n the transformer windpoints c and e toV the'same potentlal, s'o that' no current flows through the winding N, or -1 the receiver R. y

uring reception, as indicated in Fig. 24, a current I, equal to I2 flows from terminal through the receiver R-over vthe line L and through the winding N1, to terminal 7). A- current Il-L flows in parallel therewith fron` terminal c through the winding N2v to the terminal b. At this point the two curiliarj7 resistance.

(lonpming Fig. 22 with Fig. 2. it will lie 1n the former. the number of wim-l- Jngs connecting terminals` a and b. a amlm and wandel may be expressed as follows:

i i Nnb=n1 l Hurra-Fitz f Bdzng l From these equations it follows that Nac ab :n2 and Na -Nab :7l/3"??/1 these values in the general dcexpressingv the transT r', We have as thc :le substation of Fig. 22

b ubstituting sign formulae for the the following:

winding N to termlnal a. Po'- proportioned with reference to theline with herein disclosed and 2,10 companying design mola; are derwed on the ideal transformers are employed -and that .-llhc type h :in the accompanying drawing is alltel these are ideal in 'the sensethat stated heretofore )is specilication.-4 It will be 'ul'id'erstood fore', that my invention is not limited the speciic 'embodiments hereii'i illus-'f ated, but is broadly directed to providing ibstation comprising a single transformer d only one auxiliary element, yxt l'iich is so hich'iftis to` be coperatively combined,

that it isideally ecient and. substantially w hout sideA tone.

Furthermore, l do ndt' ire to limit the `design of the substations illustrated to the acformulae. These for assumption that l the component elements have noieac'tance,

niptions which are only approximately died in practice hen vparticularly if precision is desired may, therefore, lportion the substation more precisely by nO into account' the kfact that the transrmer. impedancesare finite, and that the. and the various substation elements' may e in general. sonic. rea-ctance.' The accomngjormulee however,l gire' quitesatis-v results, and the methods by which are derived will; enable one skilledl in a-rtfto'compute more precisely the subation constants when, desired. It'will be'understood that in the appended lehne, where certain elements are said to loe ugate, lor certain. impedance relations l i said to exist, since 1n practice these conditions can in. general only be approximated,

these expressions will be. satisfied 'bystruc es "substantially 'conforming thereto,l .espelly fwhere' some compromise with-'respect rthe" rigid requirements'is necessary in "der to Vdiscnnrninate againstline noise. lt fl"also be. uurlersto-od that while I have 'cifi'callyillustrated and 'describedv my innas embodied in' a 'telephone substae i, is capable of many and varied em'' inents which, render it .applicable in i lrin-fls'of signaling' systems 'and connemtly 'my invention isnot-to be li'prnitedto '-garticulartorm and use, herein disclosed'. w will; he fnrl'her-.undcrstood that in this icii'icati'on the word substation isemployedy in its-generic Sense and thatconscqnontly. ts'signilicancc is not limited to a subscrib\ crs telephone stationlmt embraces bromlly a tclepl'iofne stationr includingI Ya repeater station for relaying telephonie signale.

What is claimed is; l l. A. signaling circuit comprising a three vuwinfling induction coil and 'lour component elements consistinof a line, a transmitter, a

of substation disclosed above and a receiver andan auxiliary resistance, ofsaid component elements havinga comreceiver andan auxiliary resistance, three of said component elements having a common terminal, v the remaining component element being serial-ly connected tothe. opposite termina-l of 'one of said elements and connected to the opposite terminal of the' other two elements through the windings of Said in-duction coil, sait. remaining component element beingalso shunted by at leastaportion of the windingsof said induction coil.

. 2.' A signaling circuit comprising athree winding induction coll and fou-r component elements 'consisting ,of a line, atransmitter,

mon terminal, the remainingcomponent element being serially connected to the opposite' terminal of one. of'said elements andi-conv, nected to the opposite `terminal of the .other two elements through the windings of'said induction coil, said' remaining component element being also shunt-ed by at least a portion of the windings ofsai'd induction coil, said elements being vso lproportioned and related that ,the impedance lof' the comibinati'on comprislng the line, receiver, auxiliary resistance and induction coil, as seen from the transmitter, is equal t0 the `impedance of the transmitter.

3. A signaling circuit comprising a threewindin'g induction coil and four component elements consisting 'of a line,'a. transmitter, a receiver and an auxiliary resistance,` three of said component elements .having a, common terminal, the remaining component element 'being serially' connected to the opposite terminal ofone of said elements and connected to the opposite:A terminall of the other two elements through the windings of said inductioncoil', said remaining component element being l.also shunted by "at least a portion'l of the of said induction coil, "said elewindings' ments eing so proportionfedv and related' that the impedance 'of the combination coml prising the transmitter, r'eceiver, auxiliary rresistance, and induction coil', 'as-seen from-- ,the line, is equal to the impedance' of the line.A

4'. A signaling circuit comprising'a three winding induction coil and four 'component nent element being also shunted by at least :l portionof the vwindings of said induction coil` Said elements being so, propotimed und related that the receiver and'transmi-tter are conjugate.

`5. A sigi'ialing circuit com irising a three winding induction coil and our component elements consisting of a line, a transmitter,

a receiver and an auxiliary resistance, three of said lcomponent elements having acomnion terminal, theremaining component element being serially connected to the opposite .tciniinal'oi' one of said elements and convnected to the opposite terminal .of the other two elements througlithe windings of said induction coil, said remaining component clement being also sliunted by at least a por- `tion of thcwin'din'gs of said induction coil,

'said elements being so proportioned and. related that-the auxiliary resistance and line are conjugate.

6. A signaling circuit comprising a three Winding inductioncoil and four component elements consisting -of a line, atransmitter, 2 0 a receiver and an auxiliary resistance, three `of said component elements having a common tciiniiial,the remaining component element being serially connected to the opposite terminal of one'of said elements and con- "`nccted to the opposite terminal of the other tufo elements through the windings of said 'induction coil, said rremaining componentelement being alsoshunted by at least a portion of the `windings of s aid induction coil` said elements being so proportioned and .a-'i'cl'atcd that theimpedaiice of the combina# tion comprising the line, receiver, auxiliary resistance 4and induction coil, as seen from the transmitter, is equal to the impedance .35 ofthe transmitter, the impedance of' the con'ibination comprising the transmitter, receiver, auxiliary resistance and induction coil, as scen from the line, is equal to the impedance of the line, the receiver and trans--v 40"-initter are conjugate and the auxiliary iesistiince and line are conjugate.

7. A signaling circuit comprising a three .f windingiuduction coil and four component elements consisting of a path for the trans- 46.inission and reception ofsignals, a path iiivchilling a transmitting apparatus, a receiving apparatus, and a path including balancy,. .jing impedance, one of said three paths in- Y chuling a. winding of said induction coil,

50.said secondi iii-ci'ition'ed path-being shouted` by at 'lciista pori ion o f `lhc windings of said iiiuluction coil', said reccivii'ig apparatus be- 'lng in a .serios circuit including said. second mentioned path, and said receiving appara-V lus 'and the other'paths having a common lcrniinal. I I l, H. A signaling circuit coinprisinga. three {winding induction coil and four component elcincnts consisting o'fn palli`v for the transvQ60"'i-iiission and rcceptoi'i of signals, a path in chilling a transinitl-in'g .zi-ppai'atiis, a. `i"i\,i,c'iving V upiiiiriitus,"iiiiil n nath including balanciil'giinpcilancc, one-iii said three paths insaid second mentioned :i winding of said induction coil, 'sind second mentioned path being slhunted by at least a poi-lion of the windings of said induction coil, said receivin apparatus being in a series circuit includiiig said second mentioned path,- and said receiving apparatus and the other paths having a common terminal, said elements being so proportioned and related that the impedance of the coir'ibination comprising said induction coil, said receiving apparatiisand said first and, third mentioned paths, as seen from the second mentioned path, is equal to the impedance of said second mentioned path.

9. `A signaling circuit comprising a three winding induction coil and four component elements consisting of a path for the transmission and reception of signalsfa path including a. transmitting apparatus, a receiv-- ing 1mpedancc,one of said three-pathsincluding a winding of saidV induction coil, ath being `sl'iuiited by atleast a portion of t e windings of said induction coil, said receivin apparatus being in a series circuit inclu ing said second mentioned path, and-said receiving apparatus and the other paths having a common terminal, said Aelements being so proportioned'and related that the impedance of the combination comprising said induction coil, said receiving apparatus and said second andv third mentioned paths, 'as lseen from vsaid first mentioned path, is equal to the impedance of said lrst mentioned path.

10. A signaling circuit comprising a three winding induction coil and four component elements consistingof a path for the transmission and reception of signals, apath including a transmitting ap aratus, a receiving apparatus, and a path including balancing impedance, lone of said three paths including a windin of said induction coil, said second ineutione least a portion of the windings of said induction coil, said receiving apparatus being in a scriescrcuit including said second inentioned path, and said receiving apparatus andthe other paths having' a common terv ini-nal, said elements beings proportioned and, related that said recel in and said path-inc1nding a transmitting apparatus are. con] ugate.

, 11. A signaling circuit comprising a three winding induction coil and four component elements consisting of a path for the transmission and reception of signals, a path including a transmitting apparatus, a receiv ing apparatus, and a path including bal-` path being shouted by atV 'mission and reception of =signals,a path i'ncluding a transmitting apparatus, a. receiving apparatus, and a path including balancing said receiving'apparatus and saidpath 1nimpcdan'ce, one of said three paths including a Winding of said induction coil, said seoond mentioned path being shunted by' at least a portion of the windings of said induction coil, said receiving apparatus being in a series 'circuit including Vsaid second 'nnen-A tioned patin and .said receiving apparatus 'and the other paths hanfinggf` a common terminal, said elements being so proportioned and related that the impedance of the combiconjugate.

nations comprising said induction coil, said receiving apparatus and said first and third nientloned paths, as seen from the lsecond mentioned. path, is equal to the impedance of said second mentioned path, the impedance of the eoinbinf-x'tionl comprising said induction coil, said receiving apparatus and said second and third mentioned paths, as seen from said first' mentioned path, is equal to the impedance of said first mentioned path5 cluding a transmitting apparatusl are conjugate and said patlrinclucling balancing impedancea'nd said first mentioned path are In testimony whereof, I hare -signed my naine to this speclficatlon this 9th day of .August 1917,

' GEORGE A. CAMPBELL. 

